Layout Managers in Java : Part 3

This article explains the Box and Group layout managers in Java.

Layout Managers

Go through the following link for the layout managers discussed in the past.

http://www.c-sharpcorner.com/UploadFile/9a9e6f/layout-managers-in-java-part-2/

Now let's discuss further about layout managers.

Box layout manager

This layout manager is used to arrange the components either vertically or horizontally in a container. For this, it provides four constants that are found in the javax.swing package.

The four constants are as follows:

1. public static final int X_AXIS
2. public static final int Y_AXIS
3. public static final int LINE_AXIS
4. public static final int PAGE_AXIS

Example (X_AXIS):

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class BoxLayoutDemo extends JFrame {
   public BoxLayoutDemo()
   {
      super( "Demostrating BoxLayout" );
      final int SIZE = 3;

      Container c = getContentPane();
      c.setLayout( new BorderLayout( 30, 30 ) );

      Box boxes[] = new Box[ 4 ];

      boxes[ 0 ] = Box.createHorizontalBox();
      boxes[ 1 ] = Box.createVerticalBox();
      boxes[ 2 ] = Box.createHorizontalBox();
      boxes[ 3 ] = Box.createVerticalBox();

      // add buttons to boxes[ 0 ]
      for ( int i = 0; i < SIZE; i++ )
         boxes[ 0 ].add( new JButton( "boxes[0]: " + i ) );

      // create strut and add buttons to boxes[ 1 ]
      for ( int i = 0; i < SIZE; i++ ) {
         boxes[ 1 ].add( Box.createVerticalStrut( 25 ) );
         boxes[ 1 ].add( new JButton( "boxes[1]: " + i ) );
      }

      // create horizontal glue and add buttons to boxes[ 2 ]
      for ( int i = 0; i < SIZE; i++ ) {
         boxes[ 2 ].add( Box.createHorizontalGlue() );
         boxes[ 2 ].add( new JButton( "boxes[2]: " + i ) );
      }

      // create rigid area and add buttons to boxes[ 3 ]
      for ( int i = 0; i < SIZE; i++ ) {
         boxes[ 3 ].add(
            Box.createRigidArea( new Dimension( 12, 8 ) ) );
         boxes[ 3 ].add( new JButton( "boxes[3]: " + i ) );
      }

      // create horizontal glue and add buttons to panel
      JPanel panel = new JPanel();
      panel.setLayout(
         new BoxLayout( panel, BoxLayout.Y_AXIS ) );   // Constructor of Boxlayout class

      for ( int i = 0; i < SIZE; i++ ) {
         panel.add( Box.createGlue() );
         panel.add( new JButton( "panel: " + i ) );
      }

      // place panels on frame
      c.add( boxes[ 0 ], BorderLayout.NORTH );
      c.add( boxes[ 1 ], BorderLayout.EAST );
      c.add( boxes[ 2 ], BorderLayout.SOUTH );
      c.add( boxes[ 3 ], BorderLayout.WEST );
      c.add( panel, BorderLayout.CENTER );

      setSize( 400, 400 );
      show();
   }

   public static void main( String args[] )
   {
      BoxLayoutDemo app = new BoxLayoutDemo();

      app.addWindowListener(
         new WindowAdapter() {
            public void windowClosing( WindowEvent e )
            {
               System.exit( 0 );
            }
         }
      );
   }
}

Output:



Example (Y_AXIS):

For the BoxLayout class with Y_AXIS, we need to edit the line of code as in the following:

new BoxLayout( panel, BoxLayout.Y_AXIS ));
                             
new BoxLayout( panel, BoxLayout.X_AXIS ));

Output:



Group Layout manager

This layout manager is used to arrange the group components hierarchically to position them in a container. This is also found in the javax.swing package.

It contains the following two fields: 

1. static int DEFAULT_SIZE
2. static int PREFERRED_SIZE

Example:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class GroupLayoutDemo {
   private JFrame mainFrame;
   private JLabel headerLabel;
   private JLabel statusLabel;
   private JPanel controlPanel;
   private JLabel msglabel;

   public GroupLayoutDemo(){
      prepareGUI();
   }
      public static void main(String[] args){
      GroupLayoutDemo swingLayoutDemo = new GroupLayoutDemo();
      swingLayoutDemo.showGroupLayoutDemo();
   }

   private void prepareGUI(){
      mainFrame = new JFrame("GroupLayout Manager");
      mainFrame.setSize(400,400);
      mainFrame.setLayout(new GridLayout(3, 1));

      headerLabel = new JLabel("",JLabel.CENTER );
      statusLabel = new JLabel("",JLabel.CENTER);

      statusLabel.setSize(350,100);
      mainFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent windowEvent){
            System.exit(0);
         }
      });
      controlPanel = new JPanel();
      controlPanel.setLayout(new FlowLayout());

      mainFrame.add(headerLabel);
      mainFrame.add(controlPanel);
      mainFrame.add(statusLabel);
      mainFrame.setVisible(true);
   }
    private void showGroupLayoutDemo(){
      headerLabel.setText("Demonstration: GroupLayout Manager");

      JPanel panel = new JPanel();
      // panel.setBackground(Color.darkGray);
      panel.setSize(200,200);
      GroupLayout layout = new GroupLayout(panel);
      layout.setAutoCreateGaps(true);
      layout.setAutoCreateContainerGaps(true);
      JButton btn1 = new JButton("Button 1");
      JButton btn2 = new JButton("Button 2");
      JButton btn3 = new JButton("Button 3");

      layout.setHorizontalGroup(layout.createSequentialGroup()
         .addComponent(btn1)
         .addGroup(layout.createSequentialGroup()
            .addGroup(layout.createParallelGroup(
               GroupLayout.Alignment.CENTER)
               .addComponent(btn2)
               )
              )
               .addGroup(layout.createSequentialGroup()
            .addGroup(layout.createParallelGroup(
               GroupLayout.Alignment.CENTER)
               .addComponent(btn3)
          )
         )
      );
        layout.setVerticalGroup(layout.createSequentialGroup()
         .addComponent(btn1)
         .addComponent(btn2)
         .addComponent(btn3)
      );
      panel.setLayout(layout);
      controlPanel.add(panel);

      mainFrame.setVisible(true);
   }
}

Output:



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